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Solution conformations of pectin polysaccharides: Determination of chain characteristics by small angle neutron scattering, viscometry, and molecular modeling
Author(s) -
Cros Soizic,
Garnier Catherine,
Axelos Monique A. V.,
Imberty Anne,
Pérez Serge
Publication year - 1996
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/(sici)1097-0282(199609)39:3<339::aid-bip6>3.0.co;2-p
Subject(s) - chemistry , rhamnose , persistence length , pectin , intrinsic viscosity , monomer , polysaccharide , viscometer , dimer , crystallography , small angle x ray scattering , xyloglucan , neutron scattering , cooperativity , molecule , scattering , viscosity , thermodynamics , organic chemistry , polymer , biochemistry , physics , optics
The solution behavior of pectin polysaccharides has been investigated by small angle neutron scattering (SANS), viscosimetric, and molecular modeling studies. The samples used in the experimental study were obtained from apple and citrus and had degrees of methylation ranging from 28 to 73%, with a rhamnose content lying between 0.6 and 2.2%. Persistence lengths, derived from intrinsic viscosity measurements, ranged from 59 to 126 Å, whereas those derived by SANS were between 45 and 75 Å. These values correspond to 10–17 monomer units. The modeling simulations were performed for both homogalacturonan itself and homogalacturonan carrying various degrees of rhamnose inserts (rhamnogalacturonan). This required the evaluation of the accessible conformational space for the eight disaccharides that represent the constituent repeating segments of the homogalacturonan and rhamnogalacturonan polysaccharides. For each dimer, complete conformational analysis was accomplished using the flexible residue method of the MM3 molecular mechanics procedure and the results used to access the configurational statistics of representative pectic polysaccharide chains. For homogalacturonan, an extended chain conformation having a persistence length of 135 Å (corresponding to 30 monomers) was predicted. The inclusion of varying amounts of rhamnose units (5–25%) in the model in strict alternating sequence with galacturonate residues (equivalent to the rhamnogalacturonan “hairy region” chains) only slightly reduced the calculated persistence length. The extended overall chain conformation remained relatively unchanged as a consequence of the self‐cancellation of the kinking effects of successive paired rhamnose units. © 1996 John Wiley & Sons, Inc.